Why extremely heavy and expensive aluminum castings for RF shielding in the 400 and 800?

[Winston2022]

On 12/23/2022 at 9:47 AM, x=usr(1536) said:

Not a problem!  Here you go:

 

https://apps.fcc.gov/oetcf/eas/reports/GenericSearch.cfm

 

All you have to search for is applicant name 'Atari' and that'll give you all of Atari's FCC filings, complete with supporting documentation and correspondence.  If it's not there, it either hasn't been digitised or doesn't exist.  Enjoy!

Thanks.  6 results found if using Atari as applicant and computer as product description.  106 results just using Atari with no product description.  This is the result for any attempt to see details:

 

The following error(s) occurred while processing the requested page:

 

There are no attachments for public review associated with this application

 

SOMEWHERE online I've seen actual details from an Atari engineers notebook and documents scans on this topic, but don't remember where....

[ClausB]

4 hours ago, Winston2022 said:

SOMEWHERE online I've seen actual details from an Atari engineers notebook and documents scans on this topic, but don't remember where....

Search for DeCuir to find his notebooks.

[_The Doctor__]

Just watch any of the interviews as well, though you will still not be satisfied, I guarantee you the FCC, rf modulator and emerging standards are in play as to the classification of each device. You just keep at it, you are given answers, you won't listen, if you hear the recorded words of the guys who lived it and did it, it won't be good enough it seems. If you are as serious about this as you claim to be, it's hard to imaging you haven't heard the recounting of the engineers and designers talking about just this, it's practically legend now. Please take the time to watch such videos and recordings all the way through. I even informed you that some models and machines ceased production because of the standards that eventually rolled out.

 

Since certain cars were made at year x and they weren't required not to catch on fire or blow up how comes this car had to be made so it won't blow up, all cars should be Pinto cars!  That what I keep hearing. But see they made Pintos so why huh why huh huh why.

Edited December 30, 2022 by _The Doctor__

[Winston2022]

On 12/29/2022 at 5:21 PM, ClausB said:

Search for DeCuir to find his notebooks.

Thanks!  Found both and will be reading.

 

https://archive.org/details/JoeDecuirEngineeringNotebook1977

https://archive.org/details/JoeDecuirEngineeringNotebook1978

[Winston2022]

On 12/29/2022 at 5:51 PM, _The Doctor__ said:

Just watch any of the interviews as well, though you will still not be satisfied

I've got a large playlist of ANTIC interview MP3s I've downloaded, many of which I've listened to, but many which I haven't.  I'll go back through them looking for key individuals and listen to them again or for the first time.   

[Tickled_Pink]

On 11/29/2022 at 11:49 PM, bfollowell said:

From the way they're made, I can believe it!

 

Although the M1's armour doesn't become brittle over time.

[TGB1718]

Just found this quote from Nolan Bushnell

 

BE: Did you ever use an Atari 800 and like it?

NB: Yeah, I did. It was, in a lot of ways, a significantly superior machine to the Apple II; it had sprites. It was definitely a better game machine.

One of the problems was that Atari was so big at the time and we had such a strong relationship with Sears that they wanted FCC Type 1 approval, and that was very hard to get. So we had this big cast [metal] thing and only serial ports, and that was all to hit the FCC regulations that turned out to have no teeth at all. And so all the other PC companies, including Apple, were not Type 1 compliant, which gave them the ability to put in a good parallel bus and made the Apple II much more extensible. It was one of those things where you thought you were doing the right thing. [laughter]

BE: I guess with the Apple II they didn’t build in an RF modulator, so they didn’t have to comply with that.

NB: No, it wasn’t that. It was the actual radiation that came from the circuit board itself. And if you ever tried to look at a television set next to an Apple II, there was an awful lot of junk coming out of all of the PCs at the time. The processors were going fast enough that each of the little traces on the board would actually radiate

 

It's in this:-

http://www.vintagecomputing.com/index.php/archives/404

[_The Doctor__]

5 hours ago, TGB1718 said:

Just found this quote from Nolan Bushnell

 

BE: Did you ever use an Atari 800 and like it?

NB: Yeah, I did. It was, in a lot of ways, a significantly superior machine to the Apple II; it had sprites. It was definitely a better game machine.

One of the problems was that Atari was so big at the time and we had such a strong relationship with Sears that they wanted FCC Type 1 approval, and that was very hard to get. So we had this big cast [metal] thing and only serial ports, and that was all to hit the FCC regulations that turned out to have no teeth at all. And so all the other PC companies, including Apple, were not Type 1 compliant, which gave them the ability to put in a good parallel bus and made the Apple II much more extensible. It was one of those things where you thought you were doing the right thing. [laughter]

BE: I guess with the Apple II they didn’t build in an RF modulator, so they didn’t have to comply with that.

NB: No, it wasn’t that. It was the actual radiation that came from the circuit board itself. And if you ever tried to look at a television set next to an Apple II, there was an awful lot of junk coming out of all of the PCs at the time. The processors were going fast enough that each of the little traces on the board would actually radiate

 

It's in this:-

http://www.vintagecomputing.com/index.php/archives/404

as noted the problem was multi-fold. just add this quote with all the others and you have the a litany of reason why, and it comes back to the FCC pretty much every time for one classification(type) or another

Edited January 13, 2023 by _The Doctor__

[+Stephen]

10 minutes ago, _The Doctor__ said:

as noted the problem was multi-fold. just add this quote with all the others and you have the a litany of reason why, and it comes back to the FCC pretty much every time for one classification(type) or another

Yeah, but other machines at the time that hooked up to the TV had thin shielding, so why did Atari use such heavy casting in the 2600, 400/800?  They surely could have been much cheaper if they had right?

 

[+x=usr(1536)]

Just now, Stephen said:

Yeah, but other machines at the time that hooked up to the TV had thin shielding, so why did Atari use such heavy casting in the 2600, 400/800?  They surely could have been much cheaper if they had right?

Yes, but then it would have been impractical to use several dozen of them as cement overshoes in Mafia body disposals.  Everyone knows that.

[_The Doctor__]

Yes clearly it was because of Mafia weight requirements, in fact I think we all know what's on Jimmy Hoffa's feet . That's the real reason!

We can all rest easy now, as the lead lined refrigerators are being phased out. Getting to the bottom of lead lined refrigerators, were they mafia related, or was there another reason for them as well? Oh sorry the mind wanders, I've eaten too much lead.

Edited January 13, 2023 by _The Doctor__

[+x=usr(1536)]

1 hour ago, _The Doctor__ said:

Yes clearly it was because of Mafia weight requirements, in fact I think we all know what's on Jimmy Hoffa's feet . That's the real reason!

We can all rest easy now, as the lead lined refrigerators are being phased out.

Lake Mead is pretty close to giving up all of its secrets.  Watch for an influx of 400s, 800s, and 2600s on eBay with mud that wasn't quite cleaned out of the crevices...

1 hour ago, _The Doctor__ said:

Getting to the bottom of lead lined refrigerators, were they mafia related, or was there another reason for them as well?

Allowing protagonists to survive atomic blasts in terrible sequels, the name of which shall not be mentioned.  Other than that, I've got nothing.

1 hour ago, _The Doctor__ said:

Oh sorry the mind wanders, I've eaten too much lead.

Nothing like a few lead paint chips with a mercury chaser!

[Bryan]

I didn't see it mentioned in the thread (pardon me if it was) but I remember a story from Atari engineers that Texas Instruments was a big driving force behind the new FCC rules. They were trying to get the TI99 to market and representatives from Texas were pushing to relax the rules to help them pass testing.

[Winston2022]

On 1/13/2023 at 3:57 AM, TGB1718 said:

Just found this quote from Nolan Bushnell

 

BE: Did you ever use an Atari 800 and like it?

NB: Yeah, I did. It was, in a lot of ways, a significantly superior machine to the Apple II; it had sprites. It was definitely a better game machine.

One of the problems was that Atari was so big at the time and we had such a strong relationship with Sears that they wanted FCC Type 1 approval, and that was very hard to get. So we had this big cast [metal] thing and only serial ports, and that was all to hit the FCC regulations that turned out to have no teeth at all. And so all the other PC companies, including Apple, were not Type 1 compliant, which gave them the ability to put in a good parallel bus and made the Apple II much more extensible. It was one of those things where you thought you were doing the right thing. [laughter]

BE: I guess with the Apple II they didn’t build in an RF modulator, so they didn’t have to comply with that.

NB: No, it wasn’t that. It was the actual radiation that came from the circuit board itself. And if you ever tried to look at a television set next to an Apple II, there was an awful lot of junk coming out of all of the PCs at the time. The processors were going fast enough that each of the little traces on the board would actually radiate

 

It's in this:-

http://www.vintagecomputing.com/index.php/archives/404

Thanks!  That touches on the "what Sears demanded" for them to market Atari products I speculated about earlier in this thread.  However, as I've mentioned, the fact that the sheet metal shielded game systems on the market at the same time weren't nixed by the FCC should have been an example that Atari could have used to satisfy Sears. 

 

About his point on the relevance of the RF modulator to what emissions limits category the FCC placed a product in, of course it wasn't the emissions from the RF modulator that was an issue, it was the fact that the product with an RF modulated video output was designed and marketed to work with a standard TV set and, therefore, had to be shielded well enough to avoid RF interference at the frequencies a TV set's sensitive RF receiver received.  The Atari 8-bit machines only had RF outputs.

 

On the other hand, the reason the Apple II could legally get away with zilch shielding was because it didn't have an RF video output.  It only had a (NOT RF) composite video output because it was intended for use on a composite input computer monitor which doesn't even have sensitive TV-band RF receiver circuitry within it.  It's also the reason they could use a faster and, therefore, RF radiating data transfer bus.  You could do MODS for RF output, but that wasn't the shipped system for which Apple was responsible.

[_The Doctor__]

Thanks for sort of re saying what everyone already told you ad nauseam  but in a slightly different manor. Oh, except the 800 had a monitor port as well as rf modulator, though you are stating only had... Where as maybe the concept of more than one reason is seeping in. Did people really need to say tv band rf modulater for you? as if rf modulator wasn't enough. What did you think the computer was going to use the rf modulator for?  Wax on Wax off.

[Winston2022]

12 hours ago, _The Doctor__ said:

Thanks for sort of re saying what everyone already told you ad nauseam  but in a slightly different manor. Oh, except the 800 had a monitor port as well as rf modulator, though you are stating only had... Where as maybe the concept of more than one reason is seeping in. Did people really need to say tv band rf modulater for you? as if rf modulator wasn't enough. What did you think the computer was going to use the rf modulator for?  Wax on Wax off.

I restate in different ways because some people aren't getting this. 

 

1. The presence of a TV-band RF modulator whether composite is also available or not means the computer may be used with a TV set and that is what the Atari machines were equipped to do out of the box.

2. Back in that day, the TV used would also be attached to some kind of antenna if it was also used to watch over-air TV broadcasts. 

3. When the computer is on and even though the RF switch box is set to feed the RF signal from the computer to the TV, there is typically a 300 ohm unshielded twin lead cable going to an antenna.

4. RF from an inadequately shielded computer in proximity would be re-radiated by the antenna, interfering with other TVs not connected to the computer.  This would have been especially bad if that antenna was a gain antenna up on the roof. 

 

The Apple II did not even have TV-band RF as a video output meaning that what it was intended to be attached to would not also have a TV antenna attached.  Thus, the near total lack of shielding required for it.

Edited January 20, 2023 by Winston2022

[+x=usr(1536)]

On 1/20/2023 at 6:57 AM, Winston2022 said:

1. The presence of a TV-band RF modulator whether composite is also available or not means the computer may be used with a TV set and that is what the Atari machines were equipped to do out of the box.

Correct.  However:

On 1/20/2023 at 6:57 AM, Winston2022 said:

2. Back in that day, the TV used would also be attached to some kind of antenna if it was also used to watch over-air TV broadcasts.

Or cable TV, or a satellite receiver, or a video recorder.  This was the dawn of time for all of these devices and methods.  More:

On 1/20/2023 at 6:57 AM, Winston2022 said:

3. When the computer is on and even though the RF switch box is set to feed the RF signal from the computer to the TV, there is typically a 300 ohm unshielded twin lead cable going to an antenna.

That doesn't matter unless the switchbox is faulty, but also for other reasons.  Further:

On 1/20/2023 at 6:57 AM, Winston2022 said:

4. RF from an inadequately shielded computer in proximity would be re-radiated by the antenna, interfering with other TVs not connected to the computer.  This would have been especially bad if that antenna was a gain antenna up on the roof. 

This is incorrect.  The antenna will not passively re-radiate it; it must be directly fed with a signal in order for it to radiate.  Unless there is a short between the antenna and the computer's RF input somewhere in the switchbox, there is no way for it to transmit anything as the antenna is decoupled from the RF input when the switchbox is in the 'Computer' position.  Otherwise, in the case that you are describing, the antenna will receive the signal and likely just send it to ground.

 

Remember: the FCC is looking mainly to control unintentional radiation.  This is why the shield covers the mainboard: every item on that board is a potential radiator.  As for the RF output, all they really care about is that its output power is sufficiently low to not interfere with the marathon viewing of I Love Lucy that the next-door neighbour is in the middle of when someone wants to play Star Raiders.  Well, that and that it's not splattering across the bands that either the signal sits in or that are adjacent to it, or possibly further away.

 

FWIW, we tried the Atari-as-Pirate-TV-station experiment using both indoor and outdoor antennas as kids.  It doesn't work particularly well since there isn't enough output power in the RF modulator to really drive much of a signal, regardless of the type of antenna it may be connected to.  The disappointment upon discovering this as a child was tremendous: I had great visions of blanketing the town with SAM running in an infinite swearing loop.

[deffroe]

I bet it was stories like this that put the jeepers up my dear old dad who then refused to let me use my shiny new 800XL on the family TV on Christmas day and every day after that, incase it broke the TV.😭 Oh the memories!

[+Stephen]

4 hours ago, x=usr(1536) said:

FWIW, we tried the Atari-as-Pirate-TV-station experiment using both indoor and outdoor antennas as kids.  It doesn't work particularly well since there isn't enough output power in the RF modulator to really drive much of a signal, regardless of the type of antenna it may be connected to.  The disappointment upon discovering this as a child was tremendous: I had great visions of blanketing the town with SAM running in an infinite swearing loop.

That's fantastic!

[Winston2022]

On 1/20/2023 at 7:40 AM, x=usr(1536) said:

"That doesn't matter unless the switchbox is faulty, but also for other reasons... The antenna will not passively re-radiate it; it must be directly fed with a signal in order for it to radiate."

Incorrect.  I repeat and, once again, bold the important point.  It would be fed with a signal:

 

3. When the computer is on and even though the RF switch box is set to feed the RF signal from the computer to the TV, there is typically a 300 ohm unshielded twin lead cable going to an antenna.

 

Unshielded and NOT twisted like a twister pair WILL pick up RF from the computer and reradiate TV band frequency components through the antenna.

 

And to repeat the reason the Apple II could be virtually unshielded: it was designed and sold to be used with a composite monitor which has no TV-band RF section and, therefore, no antenna nor is it in any way connected to anything TV-band related.

 

On your pirate TV comment, of course a direct computer RF feed wouldn't produce enough power to create decent video on distant TVs, but signal quality issues could be caused to your next door neighbors' TVs from reradiated RF leakage which is what the FCC is concerned about.

 

On EMI from modern PCs:

 

https://www.arrl.org/computer

Edited January 27, 2023 by Winston2022

[+x=usr(1536)]

2 hours ago, Winston2022 said:

Incorrect.  I repeat and, once again, bold the important point.  It would be fed with a signal:

OK, we'll do this again.  I've got time to burn until the tea I'm waiting on is ready.

2 hours ago, Winston2022 said:

3. When the computer is on and even though the RF switch box is set to feed the RF signal from the computer to the TV, there is typically a 300 ohm unshielded twin lead cable going to an antenna.

You seem fixated on the idea that the presence of this cable, attached to a switchbox yet physically decoupled from a feed source, is going to cause the antenna to act as a radiator.  It's not.  If that were the case, it would be reradiating every signal broadcast at a higher power than the computer also attached to the switchbox can manage.  This would include broadcast TV and radio amongst other things.

2 hours ago, Winston2022 said:

Unshielded and NOT twisted like a twister pair WILL pick up RF from the computer and reradiate TV band frequency components through the antenna.

While it is correct that twisted pair cabling will significantly reduce the possibility of signal interference with the equipment connected to it, what you are talking about in the case of the unshielded cabling is essentially inductive coupling.  At the power levels likely to reasonably be generated by an RF modulator, the potential amount of signal radiation you could expect from that would be unlikely to be able to be measured outside of a lab in a radio-quiet environment.

 

Which brings us back to your fourth point:

On 1/20/2023 at 6:57 AM, Winston2022 said:

4. RF from an inadequately shielded computer in proximity would be re-radiated by the antenna, interfering with other TVs not connected to the computer.  This would have been especially bad if that antenna was a gain antenna up on the roof.

You're not using the terminology correctly.  Re-radiated specifically means 'transmitted again'.  This is not the same as receiving a signal.  If you mean one and not the other, use the correct wording to describe the action being referred to.  It's not reasonable to expect the reader to try to divine that from inaccurate writing.

2 hours ago, Winston2022 said:

 

On your pirate TV comment, of course a direct computer RF feed wouldn't produce enough power to create decent video on distant TVs, but signal quality issues could be caused to your next door neighbors' TVs from reradiated RF leakage which is what the FCC is concerned about.

Yes, which I already pointed out.

2 hours ago, Winston2022 said:

 

On EMI from modern PCs:

 

https://www.arrl.org/computer

A useful resource, to be sure.  Allow me to recommend one of their publications that you may find of interest:

 

https://www.arrl.org/arrl-antenna-book

[_The Doctor__]

Remember that in a perfect world people also had 75 ohm coaxial switch boxes, taroid beads/coils, and termination plugs. If you really had issues with the neighbor or making noise to interfere with the radio operator next door, you could employ those and reduce or eliminate issues as well.

 

Kyle22 had a neighbor whom he interrupted their tv with his equipment, amusing at the time, but not so nice for the neighbor. He could elaborate but I think he's no longer a part of AtariAge.

[Winston2022]

1 hour ago, x=usr(1536) said:

You seem fixated on the idea that the presence of this cable, attached to a switchbox yet physically decoupled from a feed source, is going to cause the antenna to act as a radiator.  It's not.  If that were the case, it would be reradiating every signal broadcast at a higher power than the computer also attached to the switchbox can manage.

You are the one using incorrect terminology.  A directional antenna which I gave as an example is not radiating at higher "power."  A set of rabbit ears has a small directional gain and is manually tuned by changing the length of the elements to be best at the desired TV-band RF frequencies. Any spurious RF picked up by an unshielded cable will be radiated by it.  A high gain antenna on the roof would be even worse.

1 hour ago, x=usr(1536) said:

While it is correct that twisted pair cabling will significantly reduce the possibility of signal interference with the equipment connected to it, what you are talking about in the case of the unshielded cabling is essentially inductive coupling.

Yes, I know what kind of coupling it is and I'm not talking about the RF modulator, I'm talking about the RF emitted by the PC which is broadband and would interfere with multiple TV channels.

1 hour ago, x=usr(1536) said:

You're not using the terminology correctly.  Re-radiated specifically means 'transmitted again'

HOW did I not make that obvious point clear?

1 hour ago, x=usr(1536) said:

A useful resource, to be sure.  Allow me to recommend one of their publications that you may find of interest:

I have more than one hard copy edition of it along with about a meter of other books on related topics on my bookshelf.

 

And, BTW, I can find NONE of this in any FCC document. I'm technically elaborating on a technical discussion I read somewhere years ago about how the FCC worried about more than just very short range (ex., next room) interference.

Edited January 27, 2023 by Winston2022

[+x=usr(1536)]

30 minutes ago, Winston2022 said:

You are the one using incorrect terminology.  A directional antenna which I gave as an example is not radiating at higher "power."  A set of rabbit ears has a small directional gain and is manually tuned by changing the length of the elements to be best at the desired TV-band RF frequency. Any spurious RF picked up by an unshielded cable will be radiated by it.  A high gain antenna on the roof would be even worse.

Yes, I know what kind of coupling it is and I'm not talking about the RF modulator, I'm talking about the RF emitted by the PC which is broadband and would interfere with multiple TV channels.

Having to explain your point in retrospect really doesn't help, and had you said that up front we'd be having a very different conversation.  As it is, I've ceased caring as my interest in continuing a game of moving the goalposts is less than nil.

30 minutes ago, Winston2022 said:

HOW did I not make that obvious point clear?

Through inadequate written communication.

30 minutes ago, Winston2022 said:

I have more than one hard copy edition of it along with about a meter of other books on related topics on my bookshelf.

They certainly don't seem to be helping.

[Winston2022]

They apparently weren't very RF savvy back then, but learned with time.

 

The large apertures in the sheet metal shielding shown in this (cued to the correct part) C116 video by Bil Herd of Commodore could have also been used in the earlier C64 shielding for much better ventilation and lower heat levels, thereby prolonging the life span of the run-HOT custom ICs, although the main problem with 1983 dated custom ICs in C64s was an IC manufacturing error at Commodore's MOS Technology where they put too much boron in the passivation layer causing them to fail over time:

 

 

EMI Rule-of-Thumb for Calculating Aperture Size Technical Note

 

http://cdn.lairdtech.com/home/brandworld/files/EMI Rule-of-Thumb for Calculating Aperture Size Technical Note Download.pdf